Question

For example, the default format for field 128 in OpenIso8583Rev93 is Fixed Hex 8. How would I change it to Fixed Hex 16.

Answer 1

You need to extend Iso8583Rev93 and override the template class in the constructor.

public class Iso8583Extended : Iso8583Rev93
{
    private static readonly Template ExtendedTemplate;
    static Iso8583Extended()
    {
        ExtendedTemplate = new Template();
        ExtendedTemplate[Bit._128_MAC] = FieldDescriptor.AsciiFixed(16, FieldValidators.Hex);
    }

    public Iso8583Extended():base(ExtendedTemplate)
    {
    }
}

Will do the job.